Chapter 2 - The Open Systems Interconnection Specifications (OSI)

Question 1

What is the OSI Model?

Answer 1

The OSI Model is a conceptual guideline that provides a framework for creating and implementing networking standards, devices, and internetworking schemes.

Question 2

How many layers are in the OSI Model? List each one.

Answer 2

There are 7 layers in the OSI model?

Physical, Data Link, Network, Transport, Session, Presentation, Application

Question 3

What is Layer 5?

Answer 3

Session Layer

Question 4

What is Layer 1?

Answer 4

Physical Layer

Question 5

What is Layer 7?

Answer 5

Application Layer

Question 6

What is Layer 4?

Answer 6

Transport Layer

Question 7

What is Layer 2?

Answer 7

Data Link Layer

Question 8

What is Layer 3?

Answer 8

Network Layer

Question 9

What is Layer 6?

Answer 9

Presentation Layer

Question 10

What is the Role of the Application Layer?

Answer 10

Provide a user interface

Question 11

What is the Role of the Presentation Layer?

Answer 11

Presents data; Handles processing such as encryption

Question 12

What is the Role of the Session Layer ?

Answer 12

Keeps different application’s data separate

Question 13

What is the Role of the Transport Layer?

Answer 13

Provide reliable or unreliable delivery; Performs error correction before transmit

Question 14

What is the Role of the Network Layer?

Answer 14

Provides logical addressing, which routers use for path determination

Question 15

What is the Role of the Data Link Layer?

Answer 15

Combines packets into bytes and bytes into frames; Provides access to media using MAC address; Performs error detection, not correction

Question 16

What is the Role of the Physical Layer?

Answer 16

Moves bits between devices; Specifies voltage, wire speed, and pin-out of cables

Question 17

What are the layers in the UPPER LAYERS group of the OSI and what does this group define?

Answer 17

The UPPER LAYERS are the APPLICATION, PRESENTATION, and SESSION LAYERS, which defines the rules of how the applications working within the host machine communicate with each other as well as end users.

Question 18

What are the layers in the LOWER LAYERS group of the OSI and what does this group define?

Answer 18

The LOWER LAYERS are the TRANSPORT, NETWORK, DATA LINK, and PHYSICAL LAYERS, which defines how the actual data is transmitted from end to end

Question 19

What are the functions of the Physical Layer?

Answer 19

Physical Topology; Physically, mechanically and/or electronically connect network devices; Breaks frames into binary bits; Defines the network media used

Question 20

What are the functions of the Data Link Layer?

Answer 20

Framing; Breaks data packet into frames, Manages Hardware (MAC) addresses, Defines the logical topology of the network based on IEEE 802.x standards; provides error and flow control

Question 21

What are the functions of the Network Layer?

Answer 21

Routing; Break segmented data into packets and sequences them; Assigns Logical addresses to packets; Routes packets

Question 22

What are the functions of the Transport Layer?

Answer 22

End-to-end connection; Packages data into segments; Provides flow control; Performs end-to-end transport of data

Question 23

What are the functions of the Session Layer?

Answer 23

Dialog control; Assumes a reliable virtual connection; Establishing, maintaining, synchronizing and terminating connections; Port numbers are assigned and maintained

Question 24

What are the functions of the Presentation Layer?

Answer 24

Data encryption, compression, decompression and translation services; Reformat or translate between different character sets; Provides support for recovery

Question 25

What are the functions of the Application Layer?

Answer 25

File, print, message, database, and application services; Takes data from applications; Ensures all necessary resources are available; initalizes services and the network for data transmission

Question 26

What are the two sublayers of the Data Link Layer?

Answer 26

Media Access Control (MAC) Sublayer &

Logical Link Control (LLC) Sublayer

Question 27

What is the function of the Media Access Control Sublayer?

Answer 27

The MAC sublayer is responsible for physical addressing and determining the appropriate time to place data on the network.

Question 28

What is the function of the Logical Link Control Sublayer?

Answer 28

The LLC sublayer is responsible primarily for the multiplexing of Network layer protocols

Question 29

Hubs and Repeaters operate at what layer?

Answer 29

All networking devices operate at the physical layer because they have physical connectivity, but, hubs and repeaters only operate at the PHYSICAL LAYER because they only see bits. Cable connectors, Transceivers, and NICs also function at this layer.

Question 30

Switches and Bridges operate at what layer?

Answer 30

Switches and Bridges are considered layer 2, DATA LINK Layer devices because the utilize MAC addressing

Question 31

Routers operate at what layer?

Answer 31

Routers operate at layer 3, the NETWORK LAYER because they utilize logical (IP) addressing.

Question 32

What they two types of packets used at the Network Layer?

Answer 32

Data Packets and Route-Update Packets

Question 33

What are Data Packets?

Answer 33

Data packets are used to transport user data through the internetwork. Routed protocols, such as IP and IPv6 support the data traffic

Question 34

What are Route-Update Packets?

Answer 34

Route-Update Packets utilize routing protocols such as RIP, RIPv2, OSPF, and EIGRP to help build and maintain routing tables on each router within an internetwork